import java.util.Scanner;

public class Main7 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String grade =scanner.next();

        //write your code here......
        if(grade.equals("A")){
            System.out.println("优秀");
        } else if (grade.equals("B")) {
            System.out.println("良好");
        } else if (grade.equals("C")) {
            System.out.println("及格");
        } else if (grade.equals("D")) {
            System.out.println("不及格");
        }else{
            System.out.println("未知等级");
        }
    }
}